The selection of materials for radiation detector applications is governed by fundamental physical properties of the materials. It is desirable that the material should exhibit high electrical resistivity and an excellent ability to transport charge carriers generated by external radiation. Materials that allow an applied electric field to extend through the whole volume of the crystal (i.e., full depletion) are also preferred. None of these properties can be found in high-purity and intrinsic (i.e., undoped) cadmium-zinc-tellurium (Cd1-xZnxTe (0≦x≦1)) grown by known methods.
High-purity intrinsic CdZnTe compounds typically show low electrical resistivity due to intrinsic or native defects. It is believed that such defects can include cadmium (Cd) vacancies in tellurium (Te) rich growth conditions or cadmium interstitials in cadmium rich growth conditions. In addition, an intrinsic defect of Te antisite complexes forming, often in large concentrations, a deep electronic level at the middle of the band gap. This intrinsic defect can prevent full depletion of the device when the defect is present in significant concentrations.
Unknown impurities and/or other native defects can also render the intrinsic CdZnTe compounds to have strong carrier trapping tendencies, thereby deteriorating a radiation detector's performance. When impurities, native defects, and their associations are incorporated in an uncontrolled manner, the properties of the CdZnTe compounds can vary from growth to growth and exhibit strong spatial variations within the ingots. Accordingly, there is a need for a compensation scheme that have result in CdZnTe compounds with improved carrier transport properties and depletion characteristics.